A Ni-based alloy which has presently found popular acceptance is a super heat-resisting alloy which has a Ll.sub.2 type Ni.sub.3 Al intermetallic compound precipitated or dispersed in its Ni matrix. A review of the equilibrium diagram of the conventional Ni-Al binary alloy, for example, reveals that, at room temperature, this alloy keeps Ni.sub.3 Al and Ni in coexistence when the Al content thereof falls in the range of about 23 to 28 atom% and the alloy constitutes itself a solid solution of Al in Ni when the Al content is not more than about 8 atom%. In such Ni-based Ll.sub.2 type intermetallic compounds, those which contain such compounds as Ni.sub.3 Ge, Ni.sub.3 Si, and Ni.sub.3 Al are characterized, as reported in Trans, JIM, 20, (1979), 634 and Trans, JIM, 21, (1980), 273, by acquiring higher strength at elevated temperatures than at room temperature. Accordingly, the usefulness of these intermetallic compounds at elevated temperatures has become apparent. The conventional Ni-based Ll.sub.2 type intermetallic compounds keep their crystalline structures regularized at temperature up to the neighborhood of their melting points. At room temperature, therefore, they are too brittle to be worked by ordinary methods such as are available for rolling or drawing, for example.
In view of these circumstances, studies are being actively carried out to determine a method for imparting ductility at room temperature to the Ni-based Ll.sub.2 type intermetallic compounds which cannot be molded by any other method than the casting method. Only one report on successful improvement of the ductility at room temperature of Ni.sub.3 Al by the incorporation of B is found in Journal of Japan Metal Study Society, 43 (1979), 358, 1190. According to the report, the Ll.sub.2 type intermetallic compound Ni.sub.3 Al which was brittle was provided with higher ductility and also improved strength at rupture and elongation owing to the incorporation of B. However, any improvements in mechanical properties do not appear to be great. The compound reportedly improved by the incorporation of B, when annealed at elevated temperatures, induces precipitation of B in the grain boundary and suffer notable loss of strength and ductility at elevated temperatures. Thus, this compound has no appreciable feasibility.
Separately, basic studies with single crystals are being carried out concerning the B-2 type intermetallic compounds. Since these compounds are brittle and incapable of plastic working similarly to the Ll.sub.2 type intermetallic compounds, they are now adopted in their brittle form in the manufacture of alnico magnets, for example. A report has been recently published (Glossary of Abstracts of Lectures at the Spring, 1982, meeting of Japan Metal Study Society, p. 249) to the effect that Fe-Cr-Al-Nb type alloys, when quenched and solidified by the liquid coolant method, produced B-2 type intermetallic compounds having ductility and exhibiting high electric resistance.